The electromyography has been widely used as a diagnostic method for facial muscle conditions. The aim of this study was to determine the RMS (Root Mean Square) value of the electromyographic signal of facial muscles in children with normal occlusion or cross-bite as well as to verify a possible clinical application of this parameter. "Normal group" was composed of female children with normal occlusion and "cross-bite group" was composed of female children with cross-bite. We performed quantitative electromyographic analysis of masseter and temporal muscles at rest and with maximum biting force. Our results showed that the occlusion modifications affect normal masticatory muscle function, and that the quantitative electromyography is an important tool to help diagnosing the malocclusion in female children. Considering the analysis of the results, we verified that the electromyographic rest activity of the masseter or temporal muscles in cross-bite female children is higher in relation to the rest activity of normal occlusion female children. We concluded that the RMS value of the masseteric and temporal electromyographic signal has a diagnostic value to discriminate female children with cross-bite from those with normal occlusion.Keywords: Electromyography, Malocclusion, Cross-bite. Resumo A eletromiografia tem sido amplamente utilizada como método diagnóstico de disfunções de músculos da face. O objetivo deste estudo foi determinar a tensão RMS do sinal eletromiográfico de músculos da face de crianças do sexo feminino com oclusão normal ou com mordida cruzada, visando avaliar uma possível aplicação clínica deste parâmetro. O "grupo normal" foi composto por crianças do sexo feminino com oclusão normal e o "grupo mordida cruzada" por crianças do sexo feminino com diagnóstico de mordida cruzada. Foram realizadas análises eletromiográficas quantitativas dos músculos masseter e temporal nas condições de repouso e em máxima contração voluntária isométrica (MCV). Considerando a relação da tensão RMS do sinal eletromiográfico no repouso e em MCV, nossos resultados mostraram que variações de oclusão influenciam a função muscular mastigatória normal e que a ele- Electromyography of facial muscles in cross-bite female childrenFukuda, T. Y.; Alvarez, A. S.; Nassri, L. F. G.; Godoy, C. M. G. IntroductionElectromyography consists of the graphic registration of the myoelectric signal, and it represents an important tool for quantification of muscular activity at rest and during contraction (Basmajian and De Luca, 1985;Fridlund and Cacioppo, 1986). Thus, electromyographic analysis has been widely used as a diagnostic method for muscular conditions in several situations and in different muscle functions. For example, as for the dental research, elecromyographic analysis is used to measure the electric activity of normal facial muscles, or in pathological conditions (Basmajian and De Luca, 1985;Fridlund and Cacioppo, 1986). Among the pathological conditions are the temporomandibular dysfunctions, characterized by extrin...